Break circuit for telegraph systems



Oct. 23, 1 934. R, u ms 1,978,020

BREAK CIRCUIT FOR TELEGRAPH SYSTEMS Filed Feb. 8. 1932 I i 0000M M INVENTOR HAROLD R. HUNKINS BY 7 v Awe Patented 001.23, 1934 i (UNITED STATES BREAK cmcmr FOR TELEGRAPH SYSTEMS Harold R. Hunkins, Brooklyn, N. Y., assignor to International Communications Laboratories,

Inc., Newark, N. J a corporation of New York Application February 8, 1932, Serial No. 59 1.554

4 Claims.

This invention relates to improvements in telegraph systems, and more particularly to carrier telegraphsystems in which an impulse of altere nating current is converted into an equivalent 5 direct current impulse in differential telegraph loop circuits. Such loop or subscribers loop circuits are usually associated with carrier and metallic telegraph systems. Diiferentialloopcircuits are usually opened and closed by a telegraph key when signals are sentii'om the loop to the line. They normally have the polarity of the line, as applied thereto by abattery, reversed at one end of the line by the receiving relay when signals are being received 5 fromthe main line. i e i i k In differential loopcircuits the transmission of signals from the subscribers loop to the line is accomplished by employing an open and close telegraph" key in series with the loop circuit. The 0 transmission of signals from the line to the subscribers loop is accomplished by applying polar signals to the apex of the loop circuit. These polarsignals when working in opposition to the positive battery at the distant end of the loop resultin' an open and close circuit operation as regards a neutral sounder Working in the loop circuit.

My invention is applicable to those systems wherein a single alternating current, alone or in combination with direct current, is used for the transmission of a single series of messages. It is also applicable to those systems wherein several alternating currents, alone or in combination H with a direct current, are used for the simultaneous transmission of a plurality of messages.

It is one of the primary objects of this invention to provide improved apparatus in loop circuits for enabling the loop subscriber to control the transmission of signals to the main line from his loop.

Another feature of my invention consists in the provision of positive means for transmitting a break signal from a loop circuit to a distant operator over an alternating current telegraph system.

Other purposes and objects of this invention,

together with the method and means for accomplishing the same, will suggest themselves to those versed in the art upon reading the detailed description hereinafter given, and referring to the accompanying drawing which shows a possible circuit for half-duplexing an alternating current or carrier telegraph system. In the figure, a

break relay is shown working off the contacts of a differential polar sending relay.

In the figure, 1 represents a receiving relay, 2 a break relay, 3 a sending relay, 6 represents the loop circuit which usually includes a key and a sounder in series connection, 7 represents the carrier frequency generating and modulating equipment comprising usually a vacuum tube oscillator and amplifier, 8 represents means for selecting, amplifying and rectifying the components of the carrier-receiving channel, and 9 is a differential circuit to the apex of which the signals incoming over the line are transmitted.

Referring now, more particularly, to the figure, it may be seen that one of the unique features of this circuit isthe connection of the operating winding of the break relay 2 to the armature of the sending relay 3, the marking contact of the latter relay being supplied with negative battery. The other terminal of the operating winding 5 of the break relay 2 is connected to ground at 4. The second or biasing winding of the break relay 2 may be connected to battery and ground through a variable resistance, which latter may be used to give a predetermined spacing bias. The breakrelay may have a single winding and be biased mechanically by a spring or other means.

The operation of this feature is as follows: when the local subscriber opens his loop to break the distant sender, the sending relay 3 will not leave its marking contact when the receiving relay 1 is so operated that its spacing contact is made. However, as soon as the distant operator marks and the receiving relay 1 is operated so that its marking contact is closed, the sending relay 3 will at least break its marking contact, regardless of whether or not it makes its spacing contact. This opening of the marking contact of the sending relay 3 will serve to release the break relay 2, and the spacing bias inherent in the latter will cause it to make its spacing contact, which will operate to put marking polarity or negative battery on the spacing contact of the receiving relay 1. Thus, negative battery being on both marking and spacing contacts of receiving relay 1, the local break will be positively transmitted to the line, for the tongue of sending relay 3 will be certain to make its spacing contact, which will transmit the break to the distant operator without further interruption from ized difierential loop circuit for half-duplex operation.

The arrangement of the apparatus, as given in the drawing, shows its embodiment in a loop circuit arranged for half-duplex operation and shows it as associated with a carrier terminal telegraph repeater. The incoming telegraph line is shown as terminating in a receiving relay 1. The contacts of the break relay 2 determine the polarity of the battery on the spacing contact of relay 1. When the tongue of break relay 2 is on its marking or normal contact, the signals as received in the windings of relay 1 are translated into polar signals which go to the apex of 9. The differential windings of a break relay 2 and a sending relay 3 are illustrated.

The sending relay 3 may be operated by the open and close signals from a key in the loop circuit and the battery 10 in the usual manner. Connected in the loop circuit 6 may be a relay or a sounder at the subscribers station.

While this invention has been described as embodied in a particular system and in a particular arrangement of parts, it is to be understood that this invention is capable of embodiment in other systems Without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In a telegraph signalling system, a carrier line, a carrier transmitting channel through which signals may be transmitted to said line, a carrier receiving channel to receive signals from said line, a direct current subscribers loop circuit common to said channels, a transmitting relay operable in response to a break in the subscribers loop circuit, and a break relay controlled by said transmitting relay to prevent signals received on said receiving relay from afiecting the signal transmitted by said transmitting relay in response to said break.

2. A telegraph signalling system comprising a receiving relay for receiving pulses of direct current corresponding to telegraph signals, a loop over which signals are repeated by said receiving relay, a key included in said loop, a sending relay connected between the receiving relay and the loop, a break relay controlled by said sending relay, means connecting current of one polarity to the marking contact of said receiving relay, means for connecting current of the opposite polarity to the spacing contact of said receiving relay when said break relay is in marking position, and means controlled by said break relay to reverse the polarity of battery connected to the spacing contact of said receiving relay whereby the armature of said sending relay is maintained in predetermined position while said key is open.

3. A telegraph signalling system comprising a receiving relay for receiving pulses of direct current corresponding to telegraph signals, a loop including a key, a sending relay connected between the receiving relay and the loop, a break relay normally biased to one contact and operated to the other contact under control of said sending relay, and a circuit from the armature of said break relay to a contact of said receiving relay whereby when said break relay is operated said receiving relay has the same polarity of battery on both contacts and received signals are ineffective to operate said transmitting relay.

4. A telegraph signalling system comprising a carrier receiving channel, a carrier transmitting channel, a telegraph loop, a balancing circuit therefor, a polar relay having windings in said balancing circuit and said loop, transmitting apparatus associated with said transmitting circuit and controlled by said polar relay, a receiving relay associated with said carrier receiving channel, and having its armature connected to the junction point of said polar relay windings, a source of current connected to one contact of said receiving relay, a break relay operable in response to the operation of said polar relay to connect a source of current of the same polarity to the second contact of said receiving relay to prevent the operation of said polar relay under the efiect of received signals when said loop is open.

HAROLD R. HUNKINS. 

